adaptation /ad′aptā″shən/ [L, adaptatio, act of adapting] , 1. a change or response to stress of any kind, such as inflammation of the nasal mucosa in infectious rhinitis or increased crying in a frightened child. Adaptation may be normal, self-protective, and developmental, as when a child learns to talk; it may be all-encompassing, creating further stress, as in polycythemia, which occurs naturally at high altitudes to provide more oxygen-carrying erythrocytes but may also lead to thrombosis, venous congestion, or edema. The degree and nature of adaptation shown by a patient are evaluated regularly by the members of the health care team. They constitute a measure of the effectiveness of care, the course of the disease, and the ability of the patient to cope with stress. Compare accommodation. 2. (in occupational therapy) an outcome associated with a client’s experience of relative mastery in occupational adaptation.